The present invention relates to a fan duct having containment structure for preventing penetration of the duct walls by a fan blade or parts thereof that has or have broken free from associated rotary fan driving means within the duct.
It is known to construct fan duct containment liners from materials that provide a solid or near solid structure. For example, moulded plastics, or fibrous material that is impregnated with a bonding substance, which when cured, form a solid or near solid mass of appropriate shape. The use of crushable metal lattice structures are also known, which, on being struck and deformed by a freed blade or a part thereof, absorb the kinetic energy expended by the blade.
All of the known structures have a common drawback, in that in order to ensure achievement of containment of a broken blade, the structures must have sufficient thickness which generates weight. Depending on the field of application, this might not have undue significance. However, when the field of application is in the aero engine industry, e.g. where the ducted fan is of the kind fitted to an aircraft, weight has great significance.